1. Field of the Invention
The present invention relates generally to devices which are placed in a pipeline, in-line, to stop the flow of fluid through the pipeline.
2. Description of the Related Art
In the process of removing oil or other related products from a source well, particularly in cold (adverse) environments such as Alaska, USA, it is known to inject materials under high pressure into the well in order to assist in the product removal effort. It is further known to inject differing materials in alternating fashion. Often these differing materials are incompatible, particularly in such adverse temperature environments. These materials are commonly delivered to the well through separate pipelines which come together at the well. In order to alternately provide such incompatible materials to the well as required, it is necessary to halt the flow of one material so as to allow the flow of the other, or vice versa. A need, therefore, exists for a device which prevents the flow of a material through a pipeline which can in the alternative allow such flow as required. It is a particular need for such a device for use in high pressure applications and/or in adverse environments.
Valves of many different configurations, such as gate valves or pin valves or the like have been commonly used in an effort to satisfy the above-described requirement. However, known valves include some type of mechanism which closes, or seats, to prevent flow which can be moved, or positioned, to alternately allow flow. Such repeated positioning between the valve and the seat causes wear over time. Eventually such valves begin to leak, particularly in high pressure, adverse conditions which could cause a serious problem in the above-described environment. A need, therefore, exists for a device which may alternately restrict flow and allow flow without causing wear to the sealing mechanism.
An additional limitation of valves commonly available is that they include a valve seat such that when, and if a leak occurs, the valve will allow fluid to enter the pipeline. In an effort to prevent this problem, it is common to install multiple of such valves employed in series. However, if one leaks, it vents fluid to the next valve in the pipeline. Over time, if the next valve begins to leak, fluid again enters the pipeline. A need exists for a device which includes multiple sealing surfaces wherein if one were to leak, fluid would not vent to the next sealing surface or the pipeline.